sysdev: fix missing s390 conversion

In linux-next "sysdev: Pass attribute in sysdev_class attributes show/store"
forgot to convert one place in s390 code. Here is the missing part.

Cc: Andi Kleen <ak@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

arch/s390/kernel/smp.c

@@ -1033,7 +1033,9 @@ static ssize_t __ref rescan_store(struct sysdev_class *class,
 static SYSDEV_CLASS_ATTR(rescan, 0200, NULL, rescan_store);
 #endif /* CONFIG_HOTPLUG_CPU */
 
-static ssize_t dispatching_show(struct sysdev_class *class, char *buf)
+static ssize_t dispatching_show(struct sysdev_class *class,
+				struct sysdev_class_attribute *attr,
+				char *buf)
 {
 	ssize_t count;